1. Field of the Invention
The present application relates generally to wireless networking, and more particularly to systems and methods for supporting the use of mobile devices as sensors to detect various types of environmental conditions and situations, such as weather and traffic conditions, as well as potential biological, chemical or other types of hazards, together with advanced handover (handoff) operations whereby such mobile devices may connect to different wireless networks and/or wireless network access points as needed to maintain continuity of connectivity of the mobile sensor devices with a host control or command center.
2. General Background Discussion
A. Environmental Monitoring
Environmental sensors have been developed to monitor conditions such as potential biological and chemical attacks, air quality, road conditions, traffic accidents, and so on. For example, flame detectors monitor and analyze incident radiation at selected wavelengths to determine the existence of a fire. Humidity sensors test for absolute humidity, relative humidity, or dew point in air. Moisture sensors are used to measure the moisture content in gases. Photometers and colorimeters, water quality sensors, are ion-specific computer-interfaced probes designed to determine the concentration of a solution from its color intensity. Radiation sensors are used for medical diagnoses, radioactive dating measurements, and measurements of background radiation, activity levels and radiation doses. Smoke detectors (e.g., ionization chambers and photoelectric smoke detectors) are designed to sense the products of combustion. Solar radiation sensors measure the spectral range of radiation, including global solar radiation, net solar radiation and the photosynthetic light spectrum. Temperature sensors are used to measure the temperature. UV sensors are used to detect ultraviolet power or intensity. Opacity sensors, dust sensors and visibility sensors measure the amount of light transmitted through a sample. Weather sensors are designed to measure one or multiple components of weather including wind speed and direction, rain or snow fall, solar radiation, temperature, pressure and humidity.
Many cities are deploying or considering the deployment of sensors to monitor the environment. Today, a typical approach is to deploy fixed sensors at selected geographical positions of interest. This works well when each sensor can sense a large geographical area. However, many environmental sensors can typically sense only a small area. As a result, a large number of fixed sensors are needed to cover a large city. This also means that a large and complex network infrastructure is required to connect all the sensors to monitoring centers. Furthermore, fixed sensors are prone to tampering. Accordingly, there exists a need in the art for improvement in environmental monitoring and reporting.
B. Wireless Networks
Wireless networks can incorporate a variety of types of mobile devices, such as cellular and wireless telephones, PCs (personal computers), laptop computers, wearable computers, cordless phones, pagers, headsets, printers, PDAs (personal digital assistants), etc. Mobile devices may include digital systems to secure fast wireless transmissions of voice and/or data.
Wireless LANs (WLANs) in which a mobile user can connect to a local area network (LAN) through a wireless connection may be employed for wireless communications. Wireless communications can include communications that propagate via electromagnetic waves, such as light, infrared, radio, microwave. There are a variety of different WLAN standards that currently exist, such as Bluetooth, IEEE 802.11, and HomeRF.
For example, Bluetooth products may be used to provide links between mobile computers, mobile phones, portable handheld devices, personal digital assistants (PDAs), and other mobile devices and connectivity to the Internet. Bluetooth is a computing and telecommunications industry specification that details how mobile devices can easily interconnect with each other and with non-mobile devices using a short-range wireless connection. Bluetooth creates a digital wireless protocol to address end-user problems arising from the proliferation of various mobile devices that need to keep data synchronized and consistent from one device to another, thereby allowing equipment from different vendors to work seamlessly together. Bluetooth devices may be named according to a common naming concept. For example, a Bluetooth device may possess a Bluetooth Device Name (BDN) or a name associated with a unique Bluetooth Device Address (BDA). Bluetooth devices may also participate in an Internet Protocol (IP) network. If a Bluetooth device functions on an IP network, it may be provided with an IP address and an IP (network) name. Thus, a Bluetooth Device configured to participate on an IP network may contain, e.g., a BDN, a BDA, an IP address and an IP name. The term “IP name” refers to a name corresponding to an IP address of an interface.
Similarly, IEEE 802.11 specifies technologies for wireless LANs and devices. Using 802.11, wireless networking may be accomplished with each single base station supporting several devices. In some examples, devices may come pre-equipped with wireless hardware or a user may install a separate piece of hardware, such as a card, that may include an antenna. By way of example, devices used in 802.11 typically include three notable elements, whether or not the device is an access point (AP), a mobile station (STA), a bridge, a PCMCIA card or another device: a radio transceiver; an antenna; and a MAC (Media Access Control) layer that controls packet flow between points in a network.
Wireless networks also may involve methods and protocols found in Mobile IP (Internet Protocol) systems, in PCS systems, and in other mobile network systems. With respect to Mobile IP, this involves a standard communications protocol created by the Internet Engineering Task Force (IETF). With Mobile IP, mobile device users may move across networks while maintaining their IP Address assigned once. See Request for Comments (RFC) 3344. Mobile IP enhances Internet Protocol (IP) and adds means to forward Internet traffic to mobile devices when connecting outside their home network. Mobile IP assigns each mobile node a home address on its home network and a care-of-address (CoA) that identifies the current location of the device within a network and its subnets. When a device is moved to a different network, it receives a new care-of address. A mobility agent on the home network can associate each home address with its care-of address. The mobile node can send the home agent a binding update each time it changes its care-of address by using a protocol such as Internet Control Message Protocol (ICMP).
In basic IP routing, routing mechanisms typically rely on the assumptions that each network node always has a constant attachment point to the Internet and that each node's IP address identifies the network link it is attached to. In this document, the terminology “node” includes a connection point, which can include a redistribution point or an end point for data transmissions, and which can recognize, process and/or forward communications to other nodes. For example, Internet routers can look at an IP address prefix or the like identifying a device's network. Then, at a network level, routers can look at a set of bits identifying a particular subnet. Then, at a subnet level, routers can look at a set of bits identifying a particular device. With typical mobile IP communications, if a user disconnects a mobile device from the Internet and tries to reconnect it at a new subnet, then the device has to be reconfigured with a new IP address, a proper netmask and a default router. Otherwise, routing protocols would not be able to deliver the packets properly.
C. Handovers (Handoff) of Mobile Devices
In the context of a mobile device with an IP-based wireless network interface, the mobile device needs to perform roaming or handovers when it moves from one network to another network, or from one access point of a network to another, in order to maintain session continuity, thus making it imperative for a mobile device to find immediately an appropriate point of network attachment and remain connected to ensure session continuity. With existing handover methodologies, handover is typically accomplished by performing the following sequence of protocol layer specific handovers:                First, handover takes place at the physical layer. In this regard, the mobile device switches its radio channel to a wireless base station or wireless access point in the target network.        Second, handover takes place at layer-2. In this regard, the mobile device switches its layer-2 (i.e., link-layer) connections to the target network. As explained above, the link layer or layer-2 refers to the protocol immediately below the IP-layer that carries user traffic. The mobile device performs layer-2 authentication with the target network if the target network requires such authentication.        Third, handover takes place at the IP-layer. In this regard, the mobile device obtains a local IP address from the target network, performs IP-layer authentication if required by the target network, and then performs IP-layer location update so that IP packets destined to the mobile device can be routed by the IP network to the mobile device via the target network. In some instances, one way to support IP layer location update is to use Mobile IP defined by the Internet Engineering Task Force (IETF).        Fourth, handover takes place at the application-layer. The mobile device performs necessary steps at the application layer to ensure that its application traffic will flow correctly to the applications on the mobile device via the target network. For example, when the mobile device uses the Session Initiation Protocol (SIP) defined by the IETF to manage its application-layer signaling, an application layer handover can be achieved by the mobile device updating its current location with its home SIP server. The mobile device may also need to carry out application-layer authentication with the target network if required by the target network. This is the case, for example, when the mobile device is using the IP Multimedia Subsystem (IMS) in a visited 3GPP (3rd Generation Partnership Project) wireless network, where the IMS is a SIP-based system supporting application-layer signaling and management for multimedia applications over 3GPP networks.D. Network Discovery, Media Independent Information Servers, and Handovers        
Network Discovery refers to the identification of an appropriate point of network attachment that meets the application requirements and the characteristics of the mobile device, in a timely, accurate and efficient manner. It is important for the mobile device to obtain this network information before it becomes necessary to carry out a handover or connectivity transfer operation. Network information is any information that is used by a mobile device for identifying networks, accessing networks, and seamlessly transitioning from one network connection to another. The mobile device's network connections may be homogeneous (e.g., access points belonging to the same network) or heterogeneous (e.g., access points belonging to different networks). With the proliferation of wireless network service providers, seamless handover across heterogeneous networks is becoming as important as handover between homogeneous networks. However, heterogeneous handover requires the following key capabilities:                Quick Network Discovery: To discover the most up-to-date and accurate information about the existence and availability of networks and information regarding the networks to which the mobile device may connect in a handover operation.        Quick Selection of Candidate Networks: To quickly select one network that the mobile device will prefer to use, when multiple networks are available at the same time.        
With Network Discovery, Proactive Handover Actions can be enabled. Proactive handover actions refer to performing some or all of the required handover actions before the mobile device is actually handed over to a target network to reduce delay and possible session discontinuity. For example, the mobile device may pre-acquire a local IP address and perform pre-authentication with a target network while still connected to a first network, so that when the time comes for the handover, the mobile is already assigned a valid IP address and already is authenticated with the target network.